In recent years, portable telephones, PDAs (Personal Digital Assistants), portable audio devices, and rechargeable terminal devices such as electronic toothbrushes and electronic shavers (portable electronic devices, electrical devices, and the like) have been being used more often. Within these terminal devices, a rechargeable secondary battery is installed. When a terminal voltage of the rechargeable secondary battery becomes lower than a desired value, the secondary battery should be charged. Contact and noncontact secondary-battery charging methods are employed.
In a contact charging method referred to in Japanese Registered Utility Model No. 3125341 (page 3, FIG. 1), charging is performed in a state in which a terminal for receiving power supply provided on the above-described terminal device is in contact with or a dedicated plug is mounted on a terminal for performing charging provided on a charger. In a noncontact charging method referred to in Japanese Unexamined Patent Application Publication No. 2006-203997 (page 6, FIG. 4), for example, feeding or charging is performed from a power supply device to a terminal device by means of an induced electromotive force resulting from electromagnetic induction. The power supply device is a charger compatible with these terminal devices. According to the latter charging system, there is an advantage in that feeding and charging can be performed through a simple user operation such as putting or mounting of a device body onto a charger without a power cable being connected to a terminal device. Moreover, there is an advantage in that no connector for a power supply is necessary and thus superior waterproof property and safety are obtained.
FIG. 1 is a diagram showing an exemplary internal structure of a noncontact charging system 800 according to an existing example. According to the charging system 800 shown in FIG. 1, the charging system 800 includes a power supply device 10 and a terminal device 20. The power supply device 10 includes a power transmission function unit 11. The power transmission function unit 11 includes a power cord 8 connected to an AC plug 3. An AC-DC converter 111 is connected to the power cord 8, and operates in such a manner that, for example, alternating-current power of 100 V and 50 or 60 Hz is converted into direct-current power. A high-frequency inverter 112 is connected to the AC-DC converter 111, and operates in such a manner that alternating-current power of a high frequency of about 100 kHz is generated from direct-current power. A primary coil 113 is connected to the high-frequency inverter 112, and a voltage (power) of a high frequency of about 100 kHz is applied.
On the other hand, the terminal device 20 includes a power receiving function unit 21, a circuit 22, and a rechargeable battery 23. The power receiving function unit 21 includes a secondary coil 211, an AC-DC converter 212, and a rectifier circuit 213. An alternating magnetic field of a high frequency of about 100 kHz generated by the primary coil 113 passes through the secondary coil 211. The AC-DC converter 212 is connected to the secondary coil 211, and converts alternating-current power of a high frequency induced in the secondary coil 211 into direct-current power. The rectifier circuit 213 is connected to the AC-DC converter 212 and rectifies the direct-current power, and the direct-current power is smoothed.
According to the noncontact charging system 800, in a case where high-frequency power is applied to the primary coil 113, a current flowing through the primary coil 113 generates a magnetic field in the secondary coil 211. At this time, the magnetic field changes with a change in the current. As a result, a voltage is generated in the secondary coil 211 (electromagnetic induction). Here, a voltage value induced in the secondary coil 211 can be changed via a turn ratio between the primary coil 113 and the secondary coil 211. If the number of turns of the primary coil 113 is denoted by n1, the number of turns of the secondary coil 211 is denoted by n2, a voltage applied to the primary coil 113 is denoted by V1, and a voltage applied to the secondary coil 211 is denoted by V2, the voltage V2 is expressed by Eq. (1).|V2|=n1/n2|V1|  (1)
For example, when a voltage of high-frequency power applied to the primary coil 113 is 100 V and a high-frequency voltage of 5 V is obtained in a secondary-coil side, the number of turns of the secondary coil is 1/20 the number of turns of the primary coil. Here, a generated alternating voltage is converted into a direct-current voltage by the AC-DC converter 212. Moreover, the direct-current voltage is rectified by the rectifier circuit 213. As a result of this, power supply and a charging process are performed for a signal processing unit that is not shown, the circuit 22 such as a load, and the rechargeable battery 23. Here, for efficient generation of a direct-current voltage in the terminal device 20 with respect to high-frequency power applied to the terminal device 20 from the power supply device 10, the primary coil 113 and the secondary coil 211 are provided in such a manner that the primary coil 113 and the secondary coil 211 are brought near to each other and the centers of both coils are aligned.
Moreover, in relation to a noncontact wireless electronic device, according to a data communication system utilizing a near-field wireless function, noncontact data communication processing is performed through an operation of putting or placing a terminal device on a data communication device. As terminal devices in this case, for example, a portable telephone, a digital camera, and the like are used. The data communication device (an application appliance) exchanges data such as still images, moving images, and music with these wireless electronic devices. Furthermore, as a noncontact data communication system, systems utilizing RF such as a wireless LAN, millimeter waves, and UWB are known as existing technologies.
For example, in relation to a near-field wireless system, Japanese Unexamined Patent Application Publication No. 2005-64822 (page 14, FIG. 3) discloses a wireless communication apparatus and a wireless communication system. According to this wireless communication apparatus, this wireless communication apparatus includes a data communication device and a terminal device, and data communication is performed utilizing reflected waves between the data communication device and the terminal device by a noncontact communication method. Compared with a case in which a terminal device and a data communication device are connected in a wired manner, if a device is configured like this, the degree of freedom of arrangement of terminal devices increases for the data communication device, handiness and convenience improve, and no connector is necessary. Thus, superior waterproof property and safety are obtained.
However, a wireless processing system according to an existing example has problems as in the following.
i. According to a noncontact charging system as seen in Japanese Registered Utility Model No. 3125341 (page 3, FIG. 1), Japanese Unexamined Patent Application Publication No. 2006-203997 (page 6, FIG. 4), and the like, a combination of a specific terminal device and a power supply device dedicated to the terminal device is provided. Thus, it is anticipated that since the power supply device cannot be used only for a specific terminal device, there may be a case in which many chargers are scattering around a user's house and since a charger of another device cannot be diverted, wasting of money and resources may be generated in a case where the power supply device (the charger) is lost.
ii. With respect to a problem as described above, there may be considered a method in which a general-purpose power supply device is used for various terminal devices; however, matching needs to be very strictly achieved between a wireless processing point of the power supply device and a wireless processing point of the terminal device for performing high-efficiency power supply in a noncontact manner. In this regard, a positional relationship between a primary coil of a power supply device and a secondary coil of a terminal device often varies between terminal-device models, and thus it is anticipated that alignment for performing preferable power-supply processing may be significantly difficult.
iii. According to a data communication system utilizing a near-field wireless function as seen in Japanese Unexamined Patent Application Publication No. 2005-64822 (page 14, FIG. 3), in a wireless communication method using millimeter waves, antenna directivity may be limited and the degree of freedom of arrangement of terminal devices may decrease for the data communication device. Moreover, even in a case in which a wireless communication method whose antenna directivity is generally thought of as being a wide antenna directivity, such as a wireless LAN, is used, there may be a case in which a data communication status is lowered depending on how terminal devices are placed. In this way, depending on an arrangement state of terminal devices with respect to a data communication device, there is apprehension that preferable communication cannot be executed to and from the data communication device.